The present invention relates to an apparatus for restoring the light transmittance of an image-transmitting optical fiber bundle whose image-transmitting ability has been reduced by X-ray or .gamma.-ray irradiation, and for thus restoring its usefulness in performing observations and examinations.
Fiber optic endoscopes in general use have two optical fiber bundles built therein, one for transmitting illumination light from the outside and the other for transmitting an image of the internal parts to be observed or examined. Each of said optical fiber bundles comprises an extremely large number of optical fibers with their opposed end portions rigidly secured together. They are free along their extent between the ends to allow the flexibility required to be inserted along a tortuous body passage. Fiber optic endoscopes which are used to observe or examine otherwise inaccessible body cavities are generally divided into two categories: medical and industrial.
In fiber optic endoscopes for medical use, upon inserting a fiber optic endoscope into a human body, a fluoroscopic observation is often taken to locate accurately an inserted position of the tip thereof relative to a region within the human body so as to ensure the safety of the person under examination. A certain fiber optic endoscope for medical use, for instance a duodenum endoscope, can be utilized for the purpose of endoscopic retrograde cholangiopancreatography (ERCP) examinations wherein a contrast medium is, in the case of a fluoroscopic observation, injected into the pancreatic and bile ducts through a tube which is inserted in a therapeutic instrument guide channel of a fiber optic endoscope. As described above, fiber optic endoscopes for medical use have many uses in connection with fluoroscopic observation. It is to be expected that fiber optic endoscopes will be used in connection with fluoroscopic observation more often in the future.
Consequently, an optical fiber bundle in a fiber optic endoscope used in connection with fluoroscopic observation is frequently exposed to irradiation in spite of its protective rubber tube which is a part of the fiber optic endoscope, which irradiation induces coloration thereof and decreases the light transmittance of the optical fiber bundle. A fiber optic endoscope having an image-transmitting fiber bundle with such irradiation-induced coloration may be unacceptable for observing or examining an image therethrough and so may be returned to the manufacturer for replacement of the image-transmitting fiber bundle. But an image-transmitting fiber bundle is very expensive; moreover, the replacement thereof is extremely complex and hence even more expensive.
We obtained empirically the result that the irradiation-induced coloration of an image-transmitting fiber bundle can be caused to fade by the application of visible light radiation, and that the light transmittance of said fiber bundle was then recovered to a degree acceptable for performing observations and examinations as described in detail in U.S. patent application Ser. No. 349,619, filed Feb. 17, 1982.